Spin and charge modes of the {ital t}-{ital J} ladder
- Laboratoire de Physique Quantique, Universite Paul Sabatier, 31062 Toulouse (France)
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106 (United States)
- Institute for Physics, University of Wuerzburg, D-8700 Wuerzburg (Germany)
The spin and charge excitations of the {ital t}-{ital J} ladder are studied by exact diagonalization techniques for several electron densities. The various modes are classified according to their spin (singlet or triplet excitations) and their parity under a reflection with respect to the symmetry axis along the chains and a finite-size scaling of the related gaps is performed. At low doping, formation of hole pairs leads to a spin gap for all {ital J}/{ital t} ratios. This phase is characterized by (at least) one vanishing energy mode {ital only} in the charge bonding channel when {ital K}{sub {ital x}}{r_arrow}0 consistent with the existence of superconducting pairing correlations. At larger doping the spin gap disappears. Although the antibonding modes remain gapped, low-energy {ital K}{sub {ital x}}{similar_to}0 and {ital K}{sub {ital x}}{similar_to}2{ital k}{sub {ital F}} spin and charge bonding modes are found consistent with a single-band Luttinger scenario. At sufficient low electron density and above a critical value of {ital J}/{ital t} we also expect another phase of electron pairs with gapped spin excitations.
- OSTI ID:
- 115833
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 9 Vol. 52; ISSN 0163-1829; ISSN PRBMDO
- Country of Publication:
- United States
- Language:
- English
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